Laboratory pipetter instruments are typically mannual or semi-automatic devices designed to accurately and reproducibly despense small liquid volumes typically less than 1 milliliter (ml). These devices are usually elongated instruments which, from top to bottom, typically consist of a finger activated plunger or button at the top, a hand grip in the middle, and a barrel at the bottom. The finger-activated plunger or button initiates withdrawal and dispensing of liquid. The hand grip usually houses a digital mechanism for adjusting delivery volume. The barrel houses a volumetric piston of which the distance of travel directly determines the volume of liquid delivered from the instrument. An easily removable disposable plastic tip which holds the liquid entering or exiting the pipetter is attached to the end of the pipetter barrel. This tip, typically fabricated from polyethylene or polypropylene, is clean and often sterile, and should not allow liquid to enter and contaminate the barrel containing the volumetric piston and other inner workings of the pipetter.
Occasionally during rapid pipetting operations or those involving volumes approaching the capacity of the disposable tip, liquid may be projected upward through the tip, contaminating the barrel. Depending on the application for which the pipetter is used, chemical, radiochemical, and biological contamination on both the inside and outside of the barrel may result. Contamination on the outside of the barrel is especially likely to occur during removal and dispensing of liquids from flasks, necked bottles, or test tubes. The subsequent accuracy and the ability to maintain sterility during liquid transfers may be compromised by such contamination.
Often it is desirable to remove or to deposit small volumes of liquid within deep containers, though presently available pipetters have a limited capability for reaching the bottom of such containers. The current practice is to either tilt a deep container to bring liquid near the container's orifice for pipetting of first transfer a sample of liquid to a shallow vessel using a long transfer pipet and to subsequently employ the accurate pipetter. These awkward or indirect pipetting operations are typically less desirable and less convenient than the one step pipetting operation that results when using the present invention. Further, only the short disposable tip of most pipetter instruments can be easily sterilized, leaving the remainder of the pipetter contaminated.
One object of the present invention is to reduced the incidence of contamination of pipetter's barrel by providing a replaceable and easily cleanable barrel extension tube.
Another object of this invention is to increase the reach of the pipetter into a variety of containers and especially into deep containers holding small volumes of liquid.
Another object of the present invention is to provide a clean, sterile extension tube which assures the sterility of the vessels and the liquids involved in liquid transfers.
A further object of the present invention is to provide an extension tube which can be repeatedly washed and autoclave-sterilized to reduce the risk of microbial or other contamination of the vessels and the liquids being transferred.
Still another object of the present invention is to provide a phyical extension to a pipetting instrument without significantly reducing the accuracy or reproducibility of fluid volumes transferred in routine pipetting operations.